Nucleotide sequences coding for the mikE17 gene

ABSTRACT

The invention relates to an isolated polynucleotide comprising a polynucleotide sequence chosen from the group consisting of a) polynucleotide which is identical to the extent of at least 70% to a polynucleotide which codes for a polypeptide which comprises the amino acid sequence of SEQ ID No. 2, b) polynucleotide which codes for a polypeptide which comprises an amino acid sequence which is identical to the extent of at least 70% to the amino acid sequence of SEQ ID No. 2, c) polynucleotide which is complementary to the polynucleotides of a) or b), and d) polynucleotide comprising at least 15 successive nucleotides of the polynucleotide sequence of a), b) or c),  
     and a process for the fermentative preparation of L-amino acids using  coryneform  bacteria in which at least the mikE17 gene is present in attenuated form, and the use of polynucleotides which comprise the sequences according to the invention as hybridization probes.

The invention provides nucleotide sequences from coryneform bacteriawhich code for the mikE17 gene and a process for the fermentativepreparation of amino acids using bacteria in which the mikE17 gene isattenuated.

PRIOR ART

L-Amino acids, in particular L-lysine, are used in human medicine and inthe pharmaceuticals industry, in the foodstuffs industry and veryparticularly in animal nutrition.

It is known that amino acids are prepared by fermentation from strainsof coryneform bacteria, in particular Corynebacterium glutamicum.Because of their great importance, work is constantly being undertakento improve the preparation processes. Improvements to the process canrelate to fermentation measures, such as, for example, stirring andsupply of oxygen, or the composition of the nutrient media, such as, forexample, the sugar concentration during the fermentation, or the workingup to the product form by, for example, ion exchange chromatography, orthe intrinsic output properties of the microorganism itself.

Methods of mutagenesis, selection and mutant selection are used toimprove the output properties of these microorganisms. Strains which areresistant to antimetabolites or are auxotrophic for metabolites ofregulatory importance and which produce amino acids are obtained in thismanner.

Methods of the recombinant DNA technique have also been employed forsome years for improving the strain of Corynebacterium strains whichproduce L-amino acid, by amplifying individual amino acid biosynthesisgenes and investigating the effect on the amino acid production.

OBJECT OF THE INVENTION

The inventors had the object of providing new measures for improvedfermentative preparation of amino acids.

DESCRIPTION OF THE INVENTION

Where L-amino acids or amino acids are mentioned in the following, thismeans one or more amino acids, including their salts, chosen from thegroup consisting of L-asparagine, L-threonine, L-serine, L-glutamate,L-glycine, L-alanine, L-cysteine, L-valine, L-methionine, L-isoleucine,L-leucine, L-tyrosine, L-phenylalanine, L-histidine, L-lysine,L-tryptophan and L-arginine. L-Lysine is/are particularly preferred.

When L-lysine or lysine are mentioned in the following, not only thebases but also the salts, such as e.g. lysine monohydrochloride orlysine sulfate, are meant by this.

The invention provides an isolated polynucleotide from coryneformbacteria, comprising a polynucleotide sequence which codes for themikE17 gene, chosen from the group consisting of

a) polynucleotide which is identical to the extent of at least 70% to apolynucleotide which codes for a polypeptide which comprises the aminoacid sequence of SEQ ID No. 2,

b) polynucleotide which codes for a polypeptide which comprises an aminoacid sequence which is identical to the extent of at least 70% to theamino acid sequence of SEQ ID No. 2,

c) polynucleotide which is complementary to the polynucleotides of a) orb), and

d) polynucleotide comprising at least 15 successive nucleotides of thepolynucleotide sequence of a), b) or c),

the polypeptide preferably having the activity of the transcriptionregulator MikE17.

The invention also provides the abovementioned polynucleotide, thispreferably being a DNA which is capable of replication, comprising:

(i) the nucleotide sequence, shown in SEQ ID No.1, or

(ii) at least one sequence which corresponds to sequence (i) within therange of the degeneration of the genetic code, or

(iii) at least one sequence which hybridizes with the sequencescomplementary to sequences (i) or (ii), and optionally

(iv) sense mutations of neutral function in (i).

The invention also provides:

-   a polynucleotide, in particular DNA, which is capable of replication    and comprises the nucleotide sequence as shown in SEQ ID No.1;-   a polynucleotide which codes for a polypeptide which comprises the    amino acid sequence as shown in SEQ ID No. 2;-   a vector containing parts of the polynucleotide according to the    invention, but at least 15 successive nucleotides of the sequence    claimed,-   and coryneform bacteria in which the mikE17 gene is attenuated, in    particular by an insertion or deletion.

The invention also provides polynucleotides which substantially comprisea polynucleotide sequence, which are obtainable by screening by means ofhybridization of a corresponding gene library of a coryneform bacterium,which comprises the complete gene or parts thereof, with a probe whichcomprises the sequence of the polynucleotide according to the inventionaccording to SEQ ID No.1 or a fragment thereof, and isolation of thepolynucleotide sequence mentioned.

Polynucleotides which comprise the sequences according to the inventionare suitable as hybridization probes for RNA, cDNA and DNA, in order toisolate, in the full length, nucleic acids or polynucleotides or geneswhich code for the transcription regulator MikE17 or to isolate thosenucleic acids or polynucleotides or genes which have a high similaritywith the sequence of the mikE17 gene.

Polynucleotides which comprise the sequences according to the inventionare furthermore suitable as primers with the aid of which DNA of geneswhich code for the transcription regulator MikE17 can be prepared by thepolymerase chain reaction (PCR).

Such oligonucleotides which serve as probes or primers comprise at least30, preferably at least 20, very particularly preferably at least 15successive nucleotides. Oligonucleotides which have a length of at least40 or 50 nucleotides are also suitable.

“Isolated” means separated out of its natural environment.

“Polynucleotide” in general relates to polyribonucleotides andpolydeoxyribonucleotides, it being possible for these to be non-modifiedRNA or DNA or modified RNA or DNA.

The polynucleotides according to the invention include a polynucleotideaccording to SEQ ID No. 1 or a fragment prepared therefrom and alsothose which are at least 70%, preferably at least 80% and in particularat least 90% to 95% identical to the polynucleotide according to SEQ IDNo. 1 or a fragment prepared therefrom.

“Polypeptides” are understood as meaning peptides or proteins whichcomprise two or more amino acids bonded via peptide bonds.

The polypeptides according to the invention include a polypeptideaccording to SEQ ID No. 2, in particular those with the biologicalactivity of the transcription regulator MikE17, and also those which areat least 70%, preferably at least 80% and in particular at least 90% to95% identical to the polypeptide according to SEQ ID No. 2 and have theactivity mentioned.

The invention furthermore relates to a process for the fermentativepreparation of amino acids chosen from the group consisting ofL-asparagine, L-threonine, L-serine, L-glutamate, L-glycine, L-alanine,L-cysteine, L-valine, L-methionine, L-isoleucine, L-leucine, L-tyrosine,L-phenylalanine, L-histidine, L-lysine, L-tryptophan and L-arginineusing coryneform bacteria which in particular already produce aminoacids and in which the nucleotide sequences which code for the mikE17gene are attenuated, in particular eliminated or expressed at a lowlevel.

The term “attenuation” in this connection describes the reduction orelimination of the intracellular activity of one or more enzymes(proteins) in a microorganism which are coded by the corresponding DNA,for example by using a weak promoter or using a gene or allele whichcodes for a corresponding enzyme with a low activity or inactivates thecorresponding gene or enzyme (protein), and optionally combining thesemeasures.

The microorganisms to which the present invention relates can prepareamino acids from glucose, sucrose, lactose, fructose, maltose, molasses,starch, cellulose or from glycerol and ethanol. They can berepresentatives of coryneform bacteria, in particular of the genusCorynebacterium. Of the genus Corynebacterium, there may be mentioned inparticular the species Corynebacterium glutamicum, which is known amongexperts for its ability to produce L-amino acids.

Suitable strains of the genus Corynebacterium, in particular of thespecies Corynebacterium glutamicum (C. glutamicum), are in particularthe known wild-type strains

-   -   Corynebacterium glutamicum ATCC13032    -   Corynebacterium acetoglutamicum ATCC15806    -   Corynebacterium acetoacidophilum ATCC13870    -   Corynebacterium melassecola ATCC17965    -   Corynebacterium thermoaminogenes FERM BP-1539    -   Brevibacterium flavum ATCC14067    -   Brevibacterium lactofermentum ATCC13869 and Brevibacterium        divaricatum ATCC14020        and L-amino acid-producing mutants or strains prepared        therefrom.

The new mikE17 gene from C. glutamicum which codes for the transcriptionregulator MikE17 has been isolated.

To isolate the mikE17 gene or also other genes of C. glutamicum, a genelibrary of this microorganism is first set up in Escherichia coli (E.coli). The setting up of gene libraries is described in generally knowntextbooks and handbooks. The textbook by Winnacker: Gene und Klone, EineEinführung in die Gentechnologie [Genes and Clones, An Introduction toGenetic Engineering] (Verlag Chemie, Weinheim, Germany, 1990), or thehandbook by Sambrook et al.: Molecular Cloning, A Laboratory Manual(Cold Spring Harbor Laboratory Press, 1989) may be mentioned as anexample. A well-known gene library is that of the E. coli K-12 strainW3110 set up in λ vectors by Kohara et al. (Cell 50, 495-508 (1987)).Bathe et al. (Molecular and General Genetics, 252:255-265, 1996)describe a gene library of C. glutamicum ATCC13032, which was set upwith the aid of the cosmid vector SuperCos I (Wahl et al., 1987,Proceedings of the National Academy of Sciences USA, 84:2160-2164) inthe E. coli K-12 strain NM554 (Raleigh et al., 1988, Nucleic AcidsResearch 16:1563-1575).

Börmann et al. (Molecular Microbiology 6(3), 317-326 (1992)) in turndescribe a gene library of C. glutamicum ATCC13032 using the cosmidpHC79 (Hohn and Collins, 1980, Gene 11, 291-298).

To prepare a gene library of C. glutamicum in E. coli it is alsopossible to use plasmids such as pBR322 (Bolivar, 1979, Life Sciences,25, 807-818) or pUC9 (Vieira et al., 1982, Gene, 19:259-268). Suitablehosts are, in particular, those E. coli strains which are restriction-and recombination-defective, such as, for example, the strain DH5αmcr,which has been described by Grant et al. (Proceedings of the NationalAcademy of Sciences USA, 87 (1990) 4645-4649). The long DNA fragmentscloned with the aid of cosmids or other λ vectors can then in turn besubcloned and subsequently sequenced in the usual vectors which aresuitable for DNA sequencing, such as is described e.g. by Sanger et al.(Proceedings of the National Academy of Sciences of the United States ofAmerica, 74:5463-5467, 1977).

The resulting DNA sequences can then be investigated with knownalgorithms or sequence analysis programs, such as e.g. that of Staden(Nucleic Acids Research 14, 217-232 (1986)), that of Marck (NucleicAcids Research 16, 1829-1836 (1988)) or the GCG program of Butler(Methods of Biochemical Analysis 39, 74-97 (1998)).

The new DNA sequence of C. glutamicum which codes for the mikE17 geneand which, as SEQ ID No. 1, is a constituent of the present inventionhas been found. The amino acid sequence of the corresponding protein hasfurthermore been derived from the present DNA sequence by the methodsdescribed above. The resulting amino acid sequence of the mikE17 geneproduct is shown in SEQ ID No. 2.

Coding DNA sequences which result from SEQ ID No. 1 by the degeneracy ofthe genetic code are also a constituent of the invention. In the sameway, DNA sequences which hybridize with SEQ ID No. 1 or parts of SEQ IDNo. 1 are a constituent of the invention. Conservative amino acidexchanges, such as e.g. exchange of glycine for alanine or of asparticacid for glutamic acid in proteins, are furthermore known among expertsas “sense mutations” which do not lead to a fundamental change in theactivity of the protein, i.e. are of neutral function. It is furthermoreknown that changes on the N and/or C terminus of a protein cannotsubstantially impair or can even stabilize the function thereof.Information in this context can be found by the expert, inter alia, inBen-Bassat et al. (Journal of Bacteriology 169:751-757 (1987)), inO'Regan et al. (Gene 77:237-251 (1989)), in Sahin-Toth et al. (ProteinSciences 3:240-247 (1994)), in Hochuli et al. (Bio/Technology6:1321-1325 (1988)) and in known textbooks of genetics and molecularbiology. Amino acid sequences which result in a corresponding mannerfrom SEQ ID No. 2 are also a constituent of the invention.

In the same way, DNA sequences which hybridize with SEQ ID No. 1 orparts of SEQ ID No. 1 are a constituent of the invention. Finally, DNAsequences which are prepared by the polymerase chain reaction (PCR)using primers which result from SEQ ID No. 1 are a constituent of theinvention. Such oligonucleotides typically have a length of at least 15nucleotides.

Instructions for identifying DNA sequences by means of hybridization canbe found by the expert, inter alia, in the handbook “The DIG SystemUsers Guide for Filter Hybridization” from Boehringer Mannheim GmbH(Mannheim, Germany, 1993) and in Liebl et al. (International Journal ofSystematic Bacteriology 41: 255-260 (1991)). The hybridization takesplace under stringent conditions, that is to say only hybrids in whichthe probe and target sequence, i.e. the polynucleotides treated with theprobe, are at least 70% identical are formed. It is known that thestringency of the hybridization, including the washing steps, isinfluenced or determined by varying the buffer composition, thetemperature and the salt concentration. The hybridization reaction ispreferably carried out under a relatively low stringency compared withthe washing steps (Hybaid Hybridisation Guide, Hybaid Limited,Teddington, UK, 1996).

A 5×SSC buffer at a temperature of approx. 50° C.-68° C., for example,can be employed for the hybridization reaction. Probes can alsohybridize here with polynucleotides which are less than 70% identical tothe sequence of the probe. Such hybrids are less stable and are removedby washing under stringent conditions. This can be achieved, forexample, by lowering the salt concentration to 2×SSC and optionallysubsequently 0.5×SSC (The DIG System User's Guide for FilterHybridisation, Boehringer Mannheim, Mannheim, Germany, 1995) atemperature of approx. 50° C.-68° C. being established. It is optionallypossible to lower the salt concentration to 0.1×SSC. Polynucleotidefragments which are, for example, at least 70% or at least 80% or atleast 90% to 95% identical to the sequence of the probe employed can beisolated by increasing the hybridization temperature stepwise from 50°C. to 68° C. in steps of approx. 1-2° C. Further instructions onhybridization are obtainable on the market in the form of so-called kits(e.g. DIG Easy Hyb from Roche Diagnostics GmbH, Mannheim, Germany,Catalogue No. 1603558).

Instructions for amplification of DNA sequences with the aid of thepolymerase chain reaction (PCR) can be found by the expert, inter alia,in the handbook by Gait: Oligonukleotide [sic] synthesis: A PracticalApproach (IRL Press, Oxford, UK, 1984) and in Newton and Graham: PCR(Spektrum Akademischer Verlag, Heidelberg, Germany, 1994).

It has been found that coryneform bacteria produce amino acids in animproved manner after attenuation of the mikE17 gene.

To achieve an attenuation, either the expression of the mikE17 gene orthe regulatory properties of the enzyme protein can be reduced oreliminated. The two measures can optionally be combined.

The reduction in gene expression can take place by suitable culturing orby genetic modification (mutation) of the signal structures of geneexpression. Signal structures of gene expression are, for example,repressor genes, activator genes, operators, promoters, attenuators,ribosome binding sites, the start codon and terminators. The expert canfind information on this e.g. in the patent application WO 96/15246, inBoyd and Murphy (Journal of Bacteriology 170: 5949 (1988)), in Voskuiland Chambliss (Nucleic Acids Research 26: 3548 (1998), in Jensen andHammer (Biotechnology and Bioengineering 58: 191 (1998)), in Pátek etal. (Microbiology 142: 1297 (1996)), Vasicova et al. (Journal ofBacteriology 181: 6188 (1999)) and in known textbooks of genetics andmolecular biology, such as e.g. the textbook by Knippers (“MolekulareGenetik [Molecular Genetics]”, 6th edition, Georg Thieme Verlag,Stuttgart, Germany, 1995) or that by Winnacker (“Gene und Klone [Genesand Clones]”, VCH Verlagsgesellschaft, Weinheim, Germany, 1990).

Mutations which lead to a change or reduction in the catalyticproperties of enzyme proteins are known from the prior art; exampleswhich may be mentioned are the works by Qiu and Goodman (Journal ofBiological Chemistry 272: 8611-8617 (1997)), Sugimoto et al. (BioscienceBiotechnology and Biochemistry 61: 1760-1762 (1997)) and Möckel (“DieThreonindehydratase aus Corynebacterium glutamicum: Aufhebung derallosterischen Regulation und Struktur des Enzyms [Threonine dehydratasefrom Corynebacterium glutamicum: Cancelling the allosteric regulationand structure of the enzyme]”, Reports from the Jülich Research Centre,Jü-2906, ISSN09442952, Jülich, Germany, 1994). Summarizing descriptionscan be found in known textbooks of genetics and molecular biology, suchas e.g. that by Hagemann (“Allgemeine Genetik [General Genetics]”,Gustav Fischer Verlag, Stuttgart, 1986).

Possible mutations are transitions, transversions, insertions anddeletions. Depending on the effect of the amino acid exchange on theenzyme activity, “missense mutations” or “nonsense mutations” arereferred to. Insertions or deletions of at least one base pair (bp) in agene lead to frame shift mutations, as a consequence of which incorrectamino acids are incorporated or translation is interrupted prematurely.Deletions of several codons typically lead to a complete loss of theenzyme activity. Instructions on generation of such mutations are priorart and can be found in known textbooks of genetics and molecularbiology, such as e.g. the textbook by Knippers (“Molekulare Genetik[Molecular Genetics]”, 6th edition, Georg Thieme Verlag, Stuttgart,Germany, 1995), that by Winnacker (“Gene und Klone [Genes and Clones]”,VCH Verlagsgesellschaft, Weinheim, Germany, 1990) or that by Hagemann(“Allgemeine Genetik [General Genetics]”, Gustav Fischer Verlag,Stuttgart, 1986).

A common method of mutating genes of C. glutamicum is the method of“gene disruption” and “gene replacement” described by Schwarzer andPühler (Bio/Technology 9, 84-87 (1991)).

In the method of gene disruption a central part of the coding region ofthe gene of interest is cloned in a plasmid vector which can replicatein a host (typically E. coli), but not in C. glutamicum. Possiblevectors are, for example, pSUP301 (Simon et al., Bio/Technology 1,784-791 (1983)), pK18mob or pK19mob (Schäfer et al., Gene 145, 69-73(1994)), pK18mobsacB or pK19mobsacB (Jäger et al., Journal ofBacteriology 174: 5462-65 (1992)), PGEM-T (Promega corporation, Madison,Wis., USA), pCR2.1-TOPO (Shuman (1994). Journal of Biological Chemistry269:32678-84; U.S. Pat. No. 5,487,993), pCR®Blunt (Invitrogen,Groningen, The Netherlands; Bernard et al., Journal of MolecularBiology, 234: 534-541 (1993)) or pEM1 (Schrumpf et al, 1991, Journal ofBacteriology 173:4510-4516). The plasmid vector which contains thecentral part of the coding region of the gene is then transferred intothe desired strain of C. glutamicum by conjugation or transformation.The method of conjugation is described, for example, by Schäfer et al.(Applied and Environmental Microbiology 60, 756-759 (1994)). Methods fortransformation are described, for example, by Thierbach et al. (AppliedMicrobiology and Biotechnology 29, 356-362 (1988)), Dunican and Shivnan(Bio/Technology 7, 1067-1070 (1989)) and Tauch et al. (FEMSMicrobiological Letters 123, 343-347 (1994)). After homologousrecombination by means of a “cross-over” event, the coding region of thegene in question is interrupted by the vector sequence and twoincomplete alleles are obtained, one lacking the 3′ end and one lackingthe 5′ end. This method has been used, for example, by Fitzpatrick etal. (Applied Microbiology and Biotechnology 42, 575-580 (1994)) toeliminate the recA gene of C. glutamicum.

In the method of “gene replacement”, a mutation, such as e.g. adeletion, insertion or base exchange, is established in vitro in thegene of interest. The allele prepared is in turn cloned in a vectorwhich is not replicative for C. glutamicum and this is then transferredinto the desired host of C. glutamicum by transformation or conjugation.After homologous recombination by means of a first “cross-over” eventwhich effects integration and a suitable second “cross-over” event whicheffects excision in the target gene or in the target sequence, theincorporation of the mutation or of the allele is achieved. This methodwas used, for example, by Peters-Wendisch et al. (Microbiology 144, 915-927 (1998)) to eliminate the pyc gene of C. glutamicum by a deletion.

A deletion, insertion or a base exchange can be incorporated into themikE17 gene in this manner.

In addition, it may be advantageous for the production of L-amino acidsto enhance, in particular over-express, one or more enzymes of theparticular biosynthesis pathway, of glycolysis, of anaplerosis, of thecitric acid cycle, of the pentose phosphate cycle, of amino acid exportand optionally regulatory proteins, in addition to the attenuation ofthe mikE17 gene.

The term “enhancement” in this connection describes the increase in theintracellular activity of one or more enzymes (proteins) in amicroorganism which are coded by the corresponding DNA, for example byincreasing the number of copies of the gene or genes, using a potentpromoter or using a gene or allele which codes for a correspondingenzyme (protein) having a high activity, and optionally combining thesemeasures.

Thus, for the preparation of L-amino acids, in addition to attenuationof the mikE17 gene, at the same time one or more of the genes chosenfrom the group consisting of

the dapA gene which codes for dihydrodipicolinate synthase (EP-B 0 197335),

the gap gene which codes for glyceraldehyde 3-phosphate dehydrogenase(Eikmanns (1992), Journal of Bacteriology 174:6076-6086),

the tpi gene which codes for triose phosphate isomerase (Eikmanns(1992), Journal of Bacteriology 174:6076-6086),

the pgk gene which codes for 3-phosphoglycerate kinase (Eikmanns (1992),Journal of Bacteriology 174:6076-6086),

the zwf gene which codes for glucose 6-phosphate dehydrogenase(JP-A-09224661),

the pyc gene which codes for pyruvate carboxylase (DE-A-198 31 609),

the mqo gene which codes for malate-quinone oxidoreductase (Molenaar etal., European Journal of Biochemistry 254, 395-403 (1998)),

the lysC gene which codes for a feed-back resistant aspartate kinase(Accession No.P26512; EP-B-0387527; EP-A-0699759; WO 00/63388),

the lysE gene which codes for lysine export (DE-A-195 48 222),

the hom gene which codes for homoserine dehydrogenase (EP-A 0131171),

the ilvA gene which codes for threonine dehydratase (Möckel et al.,Journal of Bacteriology (1992) 8065-8072)) or the ilvA (Fbr) allelewhich codes for a “feed back resistant” threonine dehydratase (Möckel etal., (1994) Molecular Microbiology 13: 833-842),

the ilvBN gene which codes for acetohydroxy-acid synthase (EP-B0356739),

the ilvD gene which codes for dihydroxy-acid dehydratase (Sahm andEggeling (1999) Applied and Environmental Microbiology 65: 1973-1979),

the zwa1 gene which codes for the Zwa1 protein (DE: 19959328.0, DSM13115)

can be enhanced, in particular over-expressed.

It may furthermore be advantageous for the production of amino acids, inaddition to attenuation of the mikE17 gene, at the same time for one ormore of the genes chosen from the group consisting of

the pck gene which codes for phosphoenol pyruvate carboxykinase (DE 19950 409.1, DSM 13047),

the pgi gene which codes for glucose 6-phosphate isomerase (U.S. Ser.No. 09/396,478, DSM 12969),

the poxB gene which codes for pyruvate oxidase (DE:1995 1975.7, DSM13114),

the zwa2 gene which codes for the Zwa2 protein (DE: 19959327.2, DSM13113)

to be attenuated, in particular for the expression thereof to bereduced, optionally attenuated.

In addition to attenuation of the mikE17 gene it may furthermore beadvantageous for the production of amino acids to eliminate undesirableside reactions (Nakayama: “Breeding of Amino Acid ProducingMicroorganisms”, in: Overproduction of Microbial Products, Krumphanzl,Sikyta, Vanek (eds.), Academic Press, London, UK, 1982).

The invention also provides the microorganisms prepared according to theinvention, and these can be cultured continuously or discontinuously inthe batch process (batch culture) or in the fed batch (feed process) orrepeated fed batch process (repetitive feed process) for the purpose ofproduction of L-amino acids. A summary of known culture methods isdescribed in the textbook by Chmiel (Bioprozesstechnik 1. Einführung indie Bioverfahrenstechnik [Bioprocess Technology 1. Introduction toBioprocess Technology (Gustav Fischer Verlag, Stuttgart, 1991)) or inthe textbook by Storhas (Bioreaktoren und periphere Einrichtungen[Bioreactors and Peripheral Equipment] (Vieweg Verlag,Braunschweig/Wiesbaden, 1994)).

The culture medium to be used must meet the requirements of theparticular strains in a suitable manner. Descriptions of culture mediafor various microorganisms are contained in the handbook “Manual ofMethods for General Bacteriology” of the American Society forBacteriology (Washington D.C., USA, 1981).

Sugars and carbohydrates, such as e.g. glucose, sucrose, lactose,fructose, maltose, molasses, starch and cellulose, oils and fats, suchas, for example, soya oil, sunflower oil, groundnut oil and coconut fat,fatty acids, such as, for example, palmitic acid, stearic acid andlinoleic acid, alcohols, such as, for example, glycerol and ethanol, andorganic acids, such as, for example, acetic acid, can be used as thesource of carbon. These substances can be used individually or as amixture.

Organic nitrogen-containing compounds, such as peptones, yeast extract,meat extract, malt extract, corn steep liquor, soya bean flour and urea,or inorganic compounds, such as ammonium sulfate, ammonium chloride,ammonium phosphate, ammonium carbonate and ammonium nitrate, can be usedas the source of nitrogen. The sources of nitrogen can be usedindividually or as a mixture.

Phosphoric acid, potassium dihydrogen phosphate or dipotassium hydrogenphosphate or the corresponding sodium-containing salts can be used asthe source of phosphorus. The culture medium must furthermore comprisesalts of metals, such as, for example, magnesium sulfate or ironsulfate, which are necessary for growth. Finally, essential growthsubstances, such as amino acids and vitamins, can be employed inaddition to the abovementioned substances. Suitable precursors canmoreover be added to the culture medium. The starting substancesmentioned can be added to the culture in the form of a single batch, orcan be fed in during the culture in a suitable manner.

Basic compounds, such as sodium hydroxide, potassium hydroxide, ammoniaor aqueous ammonia, or acid compounds, such as phosphoric acid orsulfuric acid, can be employed in a suitable manner to control the pH ofthe culture. Antifoams, such as, for example, fatty acid polyglycolesters, can be employed to control the development of foam. Suitablesubstances having a selective action, such as, for example, antibiotics,can be added to the medium to maintain the stability of plasmids. Tomaintain aerobic conditions, oxygen or oxygen-containing gas mixtures,such as, for example, air, are introduced into the culture. Thetemperature of the culture is usually 20° C. to 45° C., and preferably25° C. to 40° C. Culturing is continued until a maximum of the desiredproduct has formed. This target is usually reached within 10 hours to160 hours.

Methods for the determination of L-amino acids are known from the priorart. The analysis can thus be carried out, for example, as described bySpackman et al. (Analytical Chemistry, 30, (1958), 1190) by anionexchange chromatography with subsequent ninhydrin derivatization, or itcan be carried out by reversed phase HPLC, for example as described byLindroth et al. (Analytical Chemistry (1979) 51: 1167-1174).

The process according to the invention is used for fermentativepreparation of amino acids.

The following microorganism was deposited on 06.03.01 as a pure cultureat the Deutsche Sammlung für Mikrorganismen [sic] und Zellkulturen(DSMZ=German Collection of Microorganisms and Cell Cultures,Braunschweig, Germany) in accordance with the Budapest Treaty:

Escherichia coli top10/pCR2.1mikE17int as DSM 14143.

The present invention is explained in more detail in the following withthe aid of embodiment examples.

The isolation of plasmid DNA from Escherichia coli and all techniques ofrestriction, Klenow and alkaline phosphatase treatment were carried outby the method of Sambrook et al. (Molecular Cloning. A LaboratoryManual, 1989, Cold Spring Harbour [sic] Laboratory Press, Cold SpringHarbor, N.Y., USA). Methods for transformation of Escherichia coli arealso described in this handbook.

The composition of the usual nutrient media, such as LB or TY medium,can also be found in the handbook by Sambrook et al.

EXAMPLE 1

Preparation of a Genomic Cosmid Gene Library from C. Glutamicum ATCC13032

Chromosomal DNA from C. glutamicum ATCC 13032 was isolated as describedby Tauch et al. (1995, Plasmid 33:168-179) and partly cleaved with therestriction enzyme Sau3AI (Amersham Pharmacia, Freiburg, Germany,Product Description Sau3AI, Code no. 27-0913-02). The DNA fragments weredephosphorylated with shrimp alkaline phosphatase (Roche MolecularBiochemicals, Mannheim, Germany, Product Description SAP, Code no.1758250). The DNA of the cosmid vector SuperCos1 (Wahl et al. (1987),Proceedings of the National Academy of Sciences, USA 84:2160-2164),obtained from Stratagene (La Jolla, USA, Product Description SuperCos1Cosmid Vector Kit, Code no. 251301) was cleaved with the restrictionenzyme XbaI (Amersham Pharmacia, Freiburg, Germany, Product DescriptionXbaI, Code no. 27-0948-02) and likewise dephosphorylated with shrimpalkaline phosphatase.

The cosmid DNA was then cleaved with the restriction enzyme BamHI(Amersham Pharmacia, Freiburg, Germany, Product Description BamHI, Codeno. 27-0868-04). The cosmid DNA treated in this manner was mixed withthe treated ATCC13032 DNA and the batch was treated with T4 DNA ligase(Amersham Pharmacia, Freiburg, Germany, Product DescriptionT4-DNA-Ligase, Code no. 27-0870-04). The ligation mixture was thenpacked in phages with the aid of Gigapack II XL Packing Extract(Stratagene, La Jolla, USA, Product Description Gigapack II XL PackingExtract, Code no. 200217).

For infection of the E. coli strain NM554 (Raleigh et al. 1988, NucleicAcid Res. 16:1563-1575) the cells were taken up in 10 mM MgSO₄ and mixedwith an aliquot of the phage suspension. The infection and titering ofthe cosmid library were carried out as described by Sambrook et al.(1989, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor), thecells being plated out on LB agar (Lennox, 1955, Virology, 1:190)+100μg/ml ampicillin. After incubation overnight at 37° C., recombinantindividual clones were selected.

EXAMPLE 2

Isolation and Sequencing of the MikE17 gene

The cosmid DNA of an individual colony was isolated with the QiaprepSpin Miniprep Kit (Product No. 27106, Qiagen, Hilden, Germany) inaccordance with the manufacturer's instructions and partly cleaved withthe restriction enzyme Sau3AI (Amersham Pharmacia, Freiburg, Germany,Product Description Sau3AI, Product No. 27-0913-02). The DNA fragmentswere dephosphorylated with shrimp alkaline phosphatase (Roche MolecularBiochemicals, Mannheim, Germany, Product Description SAP, Product No.1758250). After separation by gel electrophoresis, the cosmid fragmentsin the size range of 1500 to 2000 bp were isolated with the QiaExII GelExtraction Kit (Product No. 20021, Qiagen, Hilden, Germany).

The DNA of the sequencing vector pZero-1, obtained from Invitrogen(Groningen, The Netherlands, Product Description Zero Background CloningKit, Product No. K2500-01) was cleaved with the restriction enzyme BamHI(Amersham Pharmacia, Freiburg, Germany, Product Description BamHI,Product No. 27-0868-04). The ligation of the cosmid fragments in thesequencing vector pZero-1 was carried out as described by Sambrook etal. (1989, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor),the DNA mixture being incubated overnight with T4 ligase (PharmaciaBiotech, Freiburg, Germany). This ligation mixture was thenelectroporated (Tauch et al. 1994, FEMS Microbiol. Letters, 123:343-7)into the E. coli strain DH5αmcr (Grant, 1990, Proceedings of theNational Academy of Sciences, U.S.A., 87:4645-4649). Letters, 123:343-7)and plated out on LB agar (Lennox, 1955, Virology, 1:190) with 50 μg/mlzeocin.

The plasmid preparation of the recombinant clones was carried out withBiorobot 9600 (Product No. 900200, Qiagen, Hilden, Germany). Thesequencing was carried out by the dideoxy chain termination method ofSanger et al. (1977, Proceedings of the National Academies of Sciences,U.S.A., 74:5463-5467) with modifications according to Zimmermann et al.(1990, Nucleic Acids Research, 18:1067). The “RR dRhodamin TerminatorCycle Sequencing Kit” from PE Applied Biosystems (Product No. 403044,Weiterstadt, Germany) was used. The separation by gel electrophoresisand analysis of the sequencing reaction were carried out in a“Rotiphoresis NF Acrylamide/Bisacrylamide” Gel (29:1) (Product No.A124.1, Roth, Karlsruhe, Germany) with the “ABI Prism 377” sequencerfrom PE Applied Biosystems (Weiterstadt, Germany).

The raw sequence data obtained were then processed using the Stadenprogram package (1986, Nucleic Acids Research, 14:217-231) version 97-0.The individual sequences of the pZerol derivatives were assembled to acontinuous contig. The computer-assisted coding region analysis [sic]were prepared with the XNIP program (Staden, 1986, Nucleic AcidsResearch, 14:217-231). Further analyses were carried out with the “BLASTsearch program” (Altschul et al., 1997, Nucleic Acids Research,25:3389-3402) against the non-redundant databank of the “National Centerfor Biotechnology Information” (NCBI, Bethesda, Md., USA).

The resulting nucleotide sequence is shown in SEQ ID No. 1. Analysis ofthe nucleotide sequence showed an open reading frame of 1425 bp, whichwas called the mikE17 gene. The mikE17 gene codes for a polypeptide of474 amino acids.

EXAMPLE 3

Preparation of an Integration Vector for Integration Mutagenesis of theMikE17 gene

From the strain ATCC 13032, chromosomal DNA was isolated by the methodof Eikmanns et al. (Microbiology 140: 1817-1828 (1994)). On the basis ofthe sequence of the mikE17 gene known for C. glutamicum from example 2,the following oligonucleotides were chosen for the polymerase chainreaction (see SEQ ID No. 3 and SEQ ID No.4):

mikE17-int1:

-   5′ AAT GGA TCA CGA TGT CAC C 3′-   mikE17-int2:-   5′ TAG TGG GTG AAG TGG AAG C 3′

The primers shown were synthesized by MWG Biotech (Ebersberg, Germany)and the PCR reaction was carried out by the standard PCR method of Inniset al. (PCR protocols. A guide to methods and applications, 1990,Academic Press) with the Taq-polymerase from Boehringer Mannheim(Germany, Product Description Taq DNA polymerase, Product No. 1 146165). With the aid of the polymerase chain reaction, the primers allowamplification of an internal fragment of the mikE17 gene 477 bp in size.The product amplified in this way was tested electrophoretically in a0.8% agarose gel.

The amplified DNA fragment was ligated with the TOPO TA Cloning Kit fromInvitrogen Corporation (Carlsbad, Calif., USA; Catalogue NumberK4500-01) in the vector pCR2.1-TOPO (Mead at al. (1991) Bio/Technology9:657-663).

The E. coli strain TOP10 was then electroporated with the ligation batch(Hanahan, In: DNA cloning. A practical approach. Vol.I. IRL-Press,Oxford, Washington D.C., USA, 1985). Selection of plasmid-carrying cellswas carried out by plating out the transformation batch on LB agar(Sambrook et al., Molecular cloning: a laboratory manual. 2^(nd) Ed.Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989),which had been supplemented with 50 mg/l kanamycin. Plasmid DNA wasisolated from a transformant with the aid of the QIAprep Spin MiniprepKit from Qiagen and checked by restriction with the restriction enzymeEcoRI and subsequent agarose gel electrophoresis (0.8%). The plasmid wascalled pCR2.1mikE17int and is shown in FIG. 1.

The following microorganism was deposited as a pure culture on06.03.2001 at the Deutsche Sammlung für Mikroorganismen und Zellkulturen(DSMZ=German Collection of Microorganisms and Cell Cultures,Braunschweig, Germany) in accordance with the Budapest Treaty:

Escherichia coli Top10/pCR2.1mikE17int as DSM 14143.

EXAMPLE 4

Integration Mutagenesis of the MikE17 Gene in the Strain DSM 5715

The vector pCR2.1mikE17int mentioned in example 3 was electroporated bythe electroporation method of Tauch et al.(FEMS Microbiological Letters,123:343-347 (1994)) in Corynebacterium glutamicum DSM 5715. The strainDSM 5715 is an AEC-resistant lysine producer (EP-A-435 132). The vectorpCR2.1mikE17int cannot replicate independently in DSM5715 and isretained in the cell only if it has integrated into the chromosome ofDSM 5715. Selection of clones with pCR2.1mikE17int integrated into thechromosome was carried out by plating out the electroporation batch onLB agar (Sambrook et al., Molecular cloning: a laboratory manual. 2^(nd)Ed. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.),which had been supplemented with 15 mg/l kanamycin.

For detection of the integration, the mikE17int fragment was labelledwith the Dig hybridization kit from Boehringer by the method of “The DIGSystem Users Guide for Filter Hybridization” of Boehringer Mannheim GmbH(Mannheim, Germany, 1993). Chromosomal DNA of a potential integrant wasisolated by the method of Eikmanns et al. (Microbiology 140: 1817-1828(1994)) and in each case cleaved with the restriction enzymes SalI,EcoRI and PstI. The fragments formed were separated by means of agarosegel electrophoresis and hybridized at 68° C. with the Dig hybrization[sic] kit from Boehringer. The plasmid pCR2.1mikE17int mentioned inexample 3 had been inserted into the chromosome of DSM5715 within thechromosomal mikE17 gene. The strain was called DSM5715::pCR2.1mikE17int.

EXAMPLE 5

Preparation of Lysine

The C. glutamicum strain DSM5715::pCR2.1mikE17int obtained in example 4was cultured in a nutrient medium suitable for the production of lysineand the lysine content in the culture supernatant was determined.

For this, the strain was first incubated on an agar plate with thecorresponding antibiotic (brain-heart agar with kanamycin (25 mg/l)[sic] for 24 hours at 33° C. Starting from this agar plate culture, apreculture was seeded (10 ml medium in a 100 ml conical flask). Thecomplete medium CgIII was used as the medium for the preculture. MediumCg III NaCl 2.5 g/l Bacto-Peptone 10 g/l Bacto-Yeast extract 10 g/lGlucose (autoclaved separately) 2% (w/v)The pH was brought to pH 7.4

Kanamycin (25 mg/l) was added to this. The preculture was incubated for16 hours at 33° C. at 240 rpm on a shaking machine. A main culture wasseeded from this preculture such that the initial OD (660 nm) of themain culture was 0.1 OD. Medium MM was used for the main culture. MediumMM CSL (corn steep liquor) 5 g/l MOPS (morpholinopropanesulfonic acid)20 g/l Glucose (autoclaved separately) 50 g/l Salts: (NH₄)₂SO₄) [sic] 25g/l KH₂PO₄ 0.1 g/l MgSO₄ * 7 H₂O 1.0 g/l CaCl₂ * 2 H₂O 10 mg/l FeSO₄ * 7H₂O 10 mg/l MnSO₄ * H₂O 5.0 mg/l Biotin (sterile-filtered) 0.3 mg/lThiamine * HCl (sterile-filtered) 0.2 mg/l Leucine (sterile-filtered)0.1 g/l CaCO₃ 25 g/l

Salts: (NH₄)₂SO₄) [sic] 25 g/l KH₂PO₄ 0.1 g/l MgSO₄ * 7 H₂O 1.0 g/lCaCl₂ * 2 H₂O 10 mg/l FeSO₄ * 7 H₂O 10 mg/l MnSO₄ * H₂O 5.0 mg/l Biotin(sterile-filtered) 0.3 mg/l Thiamine * HCl (sterile-filtered) 0.2 mg/lLeucine (sterile-filtered) 0.1 g/l CaCO₃ 25 g/l

The CSL, MOPS and the salt solution are brought to pH 7 with aqueousammonia and autoclaved. The sterile substrate and vitamin solutions arethen added, and the CaCO₃ autoclaved in the dry state is added.

Culturing is carried out in a 10 ml volume in a 100 ml conical flaskwith baffles. Kanamycin (25 mg/l) was added. Culturing was carried outat 33° C. and 80% atmospheric humidity.

After 72 hours, the OD was determined at a measurement wavelength of 660nm with a Biomek 1000 (Beckmann Instruments GmbH, Munich). The amount oflysine formed was determined with an amino acid analyzer fromEppendorf-BioTronik (Hamburg, Germany) by ion exchange chromatographyand post-column derivatization with ninhydrin detection.

The result of the experiment is shown in table 1. TABLE 1 Lysine HClStrain OD(660) g/l DSM5715 7.4 13.05 DSM5715::pCR2.1mikE17int 7.6 15.14

The following FIGURE is attached:

FIG. 1: Map of the plasmid pCR2.1mikE17int.

The abbreviations and designations used have the following meaning.

KmR: Kanamycin resistance gene

EcoRI: Cleavage site of the restriction enzyme EcoRI

PstI: Cleavage site of the restriction enzyme PstI

SalI: Cleavage site of the restriction enzyme SalI

mikE17int: Internal fragment of the mikE17 gene

ColE1: Replication origin of the plasmid ColE1

1-9. (Cancelled).
 10. A process for the fermentative preparation ofL-amino acids, in particular L-lysine, which comprises carrying out thefollowing steps: a) fermentation of the coryneform bacteria whichproduce the desired L-amino acid and in which at least the mikE17 geneor nucleotide sequences which code for it are attenuated, in particulareliminated, b) concentration of the L-amino acid in the medium or in thecells of the bacteria, and c) isolation of the L-amino acid, the biomassand/or constituents of the fermentation broth optionally remaining intheir entire amount or in portions in the product obtained in this way.11. A process as claimed in claim 10, wherein bacteria in which furthergenes of the biosynthesis pathway of the desired L-amino acids areadditionally enhanced are employed.
 12. A process as claimed in claim10, wherein bacteria in which the metabolic pathways which reduce theformation of the desired L-amino acid are at least partly eliminated areemployed.
 13. A process as claimed in claim 10, wherein the expressionof the polynucleotide(s) which code(s) for the mikE17 gene isattenuated, in particular eliminated.
 14. A process as claimed in claim10, wherein the regulatory properties of the polypeptide (enzymeprotein) for which the polynucleotide mikE17 codes are reduced.
 15. Aprocess as claimed in claim 10, wherein for the prepration of L-aminoacids, coryneform microorganisms in which at the same time one or moreof the genes chosen from the group consisting of: the dapA gene whichcodes for dihydrodipicolinate synthase, the gap gene which codes forglyceraldehyde 3-phosphate dehydrogenase, the tpi gene which codes fortriose phosphate isomerase, the pgk gene which codes for3-phosphoglycerate kinase, the zwf gene which codes for glucose6-phosphate dehydrogenase, the pyc gene which codes for pyruvatecarboxylase, the mqo gene which codes for malate-quinone oxidoreductase,the lysC gene which codes for a feed-back resistant aspartate kinase,the lysE gene which codes for lysine export, the hom gene which codesfor homoserine dehydrogenase the ilvA gene which codes for threoninedehydratase or the ilvA (Fbr) allele which codes for a feed backresistant threonine dehydratase, the ilvBN gene which codes foracetohydroxy-acid synthase, the ilvD gene which codes for dihydroxy-aciddehydratase, the zwa1 gene which codes for the Zwa1 protein is or areenhanced or over-expressed are fermented.
 16. A process as claimed inclaim 10, wherein for the preparation of L-amino acids, coryneformmicroorganisms in which at the same time one or more of the genes chosenfrom the group consisting of: the pck gene which codes for phosphoenolpyruvate carboxykinase, the pgi gene which codes for glucose 6-phosphateisomerase, the poxB gene which codes for pyruvate oxidase the zwa2 genewhich codes for the zwa2 protein is or are attenuated, in particulareliminated, are fermented.
 17. A corynebum bacterium which contains avector which carries parts of the polynucleotide as claimed in claim 1,but at least 15 successive nucleotides of the sequence claimed.
 18. Theprocess as claimed in claim 1, wherein microorganisms of the speciesCorynebacterium glutamicum are employed.
 19. A process for discoveringRNA, cDNA, and DNA in order to isolate nucleic acids, or polynucleotidesor genes which code for the transcription regulator mikE17 or have ahigh similarity with the sequence of the mikE 17 gene, which comprisesemploying the polynucleotide comprising the polynucleotide sequences asclaimed in claims 1, 2, 3 or 4 as hybridization probes.